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Characterization of Genesis Samples

Genesis Collection Types: Wafer, Concentrator Targets, Other Surfaces

The Genesis mission collected solar wind atoms for 28 months. The collectors mounted on the return capsule consisted of five arrays, the concentrator target, gold foil, polished aluminum, metallic glass, and molybdenum-coated foils.
The sample collectors are made up of fifteen materials that were chosen for bulk purity, surface cleanliness, and ability to retain the captured solar wind under space conditions. The materials chosen are listed on Table 1.
An excellent description of the materials and their intended use as collectors is given in [1].

Table 1. List of collector materials

Collector Materials

Collector Type

13C diamond (CVD)

Target

Silicon Carbide (SiC)

Target

Diamond-like Carbon Target (DOS Target)

Target

Aluminum on Sapphire (AlOS)

Wafer

Silicon, Czochralski grown (Si-CZ)

Wafer

Silicon, Float Zone (Si-FZ)

Wafer

Silicon on Sapphire (SOS)

Wafer

Germanium (Ge)

Wafer

Gold on Sapphire (AuOS)

Wafer

Sapphire (SAP)

Wafer

Carbon+Cobalt+Gold on Sapphire (CCoAuOS)

Wafer

Diamond-like Carbon on Silicon (DOS)

Wafer

Aluminum Alloy

Other Surfaces

Gold Foil

Other Surfaces

Concentrator Target Samples

The concentrator targets, their condition after return and solar wind fluence, measured and modeling, is described by [2]. The target holder, focal point of the concentrator, contained four quadrants: two SiC targets, a CVD target, and a DOS target. All targets survived intact except for the DOS target (Figs. 1 & 2).

Collector fragments can be easily identified by optical observation, except for silicon. Czochralski grown silicon is distinguished from float zone silicon by using Fourier Transform Infrared spectroscopy (FTIR) to observe a carbon-oxygen bond.

Genesis sample fragments after full characterization.

Measuring collector thickness

Different thicknesses of the collection wafers were used for the Genesis mission that were specific to each of the solar wind regimes that were sampled (bulk composition, coronal mass ejection, high speed, low speed). See Table 2. We accurately measure the thickness of collector fragments to classify each fragment by solar wind regime, taking advantage of the differences in collection wafer thickness.

A Mitutoyo Litematic VL-50® digimatic indicator is used to measure the thickness at the edge of each wafer away from any potential science testing areas. A second wafer thickness can be taken in the center of the sample using a Leica DM6000 microscope to an accuracy of ± 1.0 microns.

Genesis lab processor measures the thickness of a sample wafer to determine in which regime the solar wind was collected

Measuring sample dimensions with overview photo

Preparing to take high magnification image of a fragment

The Leica MZ9.5 stereoscope and the Leica DM6000 microscope are used to take detailed images of each sample. Canvas 12 software is used to measure and calculate the sample length, width and area based on the scaled images.